The present invention relates generally to the fabrication of fiber-reinforced plastic (FRP) components using the vacuum-assist-resin-transfer-mold (VARTM) approach, and, more particularly, to an improved method thereof.
In VARTM processing, dry fiber strips, plies, or mats are applied over a mold surface to form a fiber lay up of desired thickness. In addition, one or more closed-cell core layers may be included. A flexible, gas impervious sheet, liner, or bag is placed over the lay up to form a sealed vacuum envelope over the mold. Catalyzed resin is then injected into the mold through a series of disposable supply lines and conduits placed on or adjacent to the fiber lay up and allowed to “wet” the fiber mat to produce a fiber-reinforced plastic laminate.
A major disadvantage of this approach includes long setup times for the injection and vacuum ports/runners. Common practice is to assemble a series of tubes and connectors to a helical spring to create a manifold; see e.g., U.S. Pat. No. 4,902,215, issued to William Seeman on Feb. 20, 1990. This labor-intensive operation requires more up-front effort for fabrication and placement of these manifolds prior to the bagging operations. Another disadvantage is the long mold-filling time, resulting in elevated costs for consumable materials as well as touch labor. For large parts, the flow issue is increasingly problematic with the risk of resin cure prior to total mold fill, resulting in very expensive scrap parts.
Conventionally, there have been a number of ways to reduce the time standards associated with the VARTM process. Current techniques call for the use of a distribution media constituted of spaced-apart lines running crisscross one with another forming two sets of parallel lines which act as vertical pillars creating lateral passageways running in the direction of flow; see e.g., U.S. Pat. No. 4,902,215, issued to William Seeman on Feb. 20, 1990. Another design employs the use of resin conduits integral to a reusable silicone bag; see e.g., U.S. Pat. No. 5,316,462, issued to William Seeman on May 31, 1994.
Each of these techniques has drawbacks. A distribution media with lateral passageways provides a directionalized flow, leaving a potential for local dry spots throughout the laminate, which may result in costly rework or scrap. A reusable bag with integral resin conduits is specific to the geometry to be fabricated. This approach thereby yields a geometry-specific system, requiring specialized bags for different shapes and sizes. Both techniques increase skill and time requirements to fabricate a resultant article to meet the desired standards for cost and quality.
What is needed is a means of providing a non-directional, high-permeability system for VARTM applications, with a universal, modular, and reusable port-runner device.